1. Field of the Invention
The present invention relates to a device for transmitting over a distance the angular position of rotary elements and in particular indicator drums of a meter or counter. It concerns more particularly fluid or electrical energy consumption meters the indications of which are given by rotary drums.
2. Description of the Prior Art
The devices for the transmission over a distance of the indications of a meter are adapted to reduce the time for reading the meter and the expense of invoicing the consumed amounts of fluid or electrical energy. Indeed, in the absence of such a device the inspection of the meters results in loss of time for the personnel whose function is to effect these readings, since the counters are usually placed in premises and the personnel whose function is to read the meters must often carry out several operations. Moreover, the invoicing requires several recordings of the reading figures and of the number of the subscriber, which entails serious risks of error.
Devices for the transmission over a distance of the indications of a meter are known. The most perfected of these devices only consume electrical energy at the moment of the measurements. This is particularly the case of devices of the type comprising, connected to an exterior socket -- to which may be connected an apparatus for reading and generating current and decoding -- on one hand, a coding unit comprising for each rotary element a cam which is recessed in steps and connected to rotate with its rotary element, a follower elastically biased toward the stepped cam, and a smooth cam connected to drive means and adapted to maintain the follower away from the stepped cam outside the reading periods, and, on the other hand, a device for detecting the movement of the follower.
A known device of this type is described in particular in the West German Offenlegungsschrift No. 1,939,533. In this device, at the moment of the measurement, the smooth cam is rotated in the direction of decreasing radii; the follower consequently moves, in constant cooperation with the smooth cam, until it comes into abutment with one of the sectors of the stepped cam. The extent of this movement of the follower is measured by the detecting device which sends pulses transmitted to the counter of the reading apparatus.
This known device has the following drawbacks: first, the continuous movement of the follower between its position in which it bears against the stepped cam is amplified by gearing before it is measured and this gives rise to problems due to play in the transmission at the start and end of the movement. This play adversely affects the precision in the measurement and might lead to a different result which differs to the extent of at least one unit, more or less, with respect to the actual indication of the indicator drum. Moreover, even if the follower constantly cooperates with the smooth cam, it comes in contact with the stepped cam relatively suddenly, and this might result in rebounds and vibrations of the follower which are liable to cause the detecting device to produce parasitic pulses, this detecting device being of necessity very sensitive since one pulse corresponds to a very small movement of the follower. It is easy to imagine the seriousness of such parasitic pulses when it concerns the measurement of, for example, the indication of the meter indicator drum corresponding to the tens of thousands.